The invention discloses an installation method for a large bridge crane. The installation method for the large bridge crane comprises the following steps: S1, carrying out construction preparation; S2, assembling a main beam at a left side and a main beam at a right side respectively, assembling two secondary beams at the middle part, and end beams, and installing heat-isolation plates below the main beam at the left side, the main beam at the right side, and the secondary beams; S3, sequentially lifting the main beam at one side, and the secondary beams and the end beams which are integrally assembled, and fixedly installing the main beam at the side, and the end beams; S4, lifting the main beam at the other side; and S5, sequentially lifting a secondary trolley and a main trolley. According to the installation method for the large bridge crane, which is disclosed by the invention, the maim beams, the secondary beams and the end beams are lifted by virtue of an automobile crane, and the main trolley is lifted in the form of cooperating the automobile crane with a traction device, thus consumed number of automobile crane groups, and the labour cost of operation are reduced; and one automobile crane is used for lifting, thus lifting difficulty for the main trolley can be reduced, and construction safety and quality are guaranteed.